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Friday, April 16, 2010

Seedlings Saved

Garden pests come in all shapes and sizes, but one thing’s for certain: there’s not a plant on earth without a nemesis. In many ways, this is a good thing, considering the need for balance in the universe. But when the balancing act occurs on my vegetable seedlings, I’m in no mood to think globally. This is war.

My newly transplanted seedlings are infested with fungus gnats. Sounds gross, right? Well, it’s not pretty, but it’s not as damaging as it seems. The gnats’ larva are sometimes found in commercial potting soil. They propagate rapidly in moist conditions. You might not be aware of the larva until they reach the adult fly stage, which is often too late. While their lifecycle is relatively short, these flies lay more than 100 eggs per day. The tiny flies stick close to the leaves, while their larva feed on organic matter in the soil. A heavy infestation could lead to seedling root damage.

I scoured the internet for information on how to get rid of these pests. Remedies range from placing a moist slice of potato on the soil surface, to yellow sticky tape, to beneficial nematodes. Unsure of the severity of the infestation, and too emotional to make a decision, I decided to consult the plant clinic at Merrifield Garden Center. A kindly woman with the voice of gardeners past cautioned against anything homeopathic or potentially poisonous. She calmly said, “Now you don’t see any damage to your seedlings, do you?”, and in fact, I did not. She explained that while the larva may eventually feed on roots, they are only feeding on the soil at this point. Since I’ll be putting the seedlings outdoors in just a couple of weeks, she recommended the least invasive remedy: yellow sticky tape, placed in a nearby window. The flies are attracted to the color yellow. Sticking to the tape will cut down on reproduction. She also suggested setting the trays outdoors for a couple of hours to provide some ventilation.

So how could this have been prevented? The larva, which were present in the potting mix I used, thrive in moist conditions. Instead of spraying my seedlings so that moisture didn’t collect at the bottom of the tray, I watered them. Wrong, wrong, wrong. Did I know this? Yes, but we were going away for the weekend, and I thought I could stretch them for a few days by giving a little extra water. Poor drainage resulted in a breeding ground for the gnats. The solution: next time we go away, I’ll arm my six-year-old neighbor with a spray bottle and trust that she follows directions more closely than I do! Granted, this won't prevent fungus gnats, but it will deter them. I'll also start making my own potting mix: